Quantitative bedrock geology of Brazil

Abstract

[1] We quantitatively analyze the area-age distribution of sedimentary, igneous, metamorphic, and ultramafic bedrock on the basis of data from the digital geologic map of Brazil, published as a GIS map by the Brazilian Geological Survey. Bedrock units exclusively encompassing sedimentary rocks, igneous rocks, or metamorphic rocks cover 40.4%, 31.5%, and 17.7%, respectively, of the total bedrock area. These numbers have to be considered minimum estimates of the areal abundance of sedimentary, igneous, and metamorphic bedrock because polygons defined by mixed lithologies cover $8.5-9.5% of the total bedrock area. These mixed units are sedimentary rocks with igneous and/or metamorphic contributions (1.4%), metamorphic rocks with sedimentary contributions (1.2%), metamorphic rocks with igneous contributions (1.5%), igneous rocks with sedimentary and/or metamorphic contributions (4.4%), and ultramafic units with sedimentary, igneous, and/or metamorphic contributions ($1-2%). The average ages of major lithologic units, weighted according to bedrock area, are as follows: sedimentary rocks (average stratigraphic age of 248 ± 5 [1s] Myr; median stratigraphic age of 87.5 Myr), igneous rocks (1153 ± 13 [1s] Myr), metamorphic rocks (1678 ± 30 [1s] Myr), and ultramafic rocks ($1227 ± 25 [1s] Myr). The average bedrock age of Brazil is 946 ± 7 [1s] Myr. The range in lithologic composition and age structure of the various bedrock units reflects the complex tectonic makeup of Brazil that ranges from Neogene sedimentary cover in the Amazon Basin to Precambrian cratons (Guyana and Brazilian shields) and Transamazonian greenstone belts. The average spatial resolution of the data is 232 km 2 polygon À1 and is sufficient to perform area-age analyses of individual river drainage basins larger than $5,000 km 2 .Components: 3797 words, 3 figures, 1 table.

Quantitative bedrock geology of the continents and large‐scale drainage regions

“…It should be noted that at the given temporal resolution of the data, the choice of timescale is of minor importance to the data quality. The coarser temporal resolution of the global data implies a larger uncertainty in the calculated area‐age relationships compared to previously analyzed data [ Peucker‐Ehrenbrink and Miller , 2002, 2003, 2004, 2007]. As we assign average ages of lithologic units based on the midpoint between the upper and lower age boundaries, a coarser temporal resolution tends to overestimate average ages compared to bedrock data with higher temporal resolution.…”

“…The methods used are very similar to those employed in our previous studies [ Peucker‐Ehrenbrink and Miller , 2002, 2003, 2004, 2007]. Relevant projection parameters and software used are summarized in Text S1.…”

“…[2] We are extending our previous characterizations of bedrock composition in the conterminous United States of America [Peucker-Ehrenbrink and Miller, 2002], Alaska and Canada [Peucker-Ehrenbrink and Miller, 2003], East and Southeast Asia [Peucker-Ehrenbrink and Miller, 2003] and Brazil [Peucker-Ehrenbrink and Miller, 2007] to the entire world land surface in an attempt to improve global estimates of the lithologic compo-sition and age distribution of bedrock using modern geographic information systems and digital geologic maps. We also use the delineation of 19 large-scale drainage regions [Graham et al, 1999] to compute the lithologic variability of bedrock draining into regions of the world's oceans.…”

Emmanuelia, a new genus of lobarioid lichen-forming fungi (Ascomycota: Peltigerales): phylogeny and synopsis of accepted species

“…Notably, the crown divergence time for Emmanuelia coincides with the onset of the uplift of the northern Andes (Hoorn et al 2010). The latter may explain the rather recent diversification of genera such as Lobariella (Moncada et al 2013), but most of the Emmanuelia species occur in the Atlantic Forest of southeastern Brazil, in a geologically much older formation (Peucker-Ehrenbrink & Miller 2007;Brotzu et al 2007;Colombo & Joly 2010). Possibly the recent diversification of Emmanuelia largely in the Atlantic Forest, with subsequent expansion northwards, is related to paleoclimatic events, as apparent from other groups of organisms in this biome with similarly recent diversification times (e.g., Fouquet et al 2012;Batalha-Filho et al 2013;Machado et al 2018).…”